The aspartic protease from Rhizopus chinensis has been analyzed as a complex with the inhibitor pepstatin. A mechanism of substrate binding and cleavage has been proposed. Cyrstals have been obtained of mouse renin. Some preliminary data collection has begun with the enzyme S-adenosyl methionine synthetase. The x-ray structure of bovine ribonuclease A has been refined to 2.0 a resolution. The neutron diffraction investigation of this enzyme has been completed at 2.8 A and is being extended to 2.0 A.